[webapi] Modify the AudioContext construction for WebAudio

Impacted Suites: tct-webaudio-w3c-tests
Impacted TCs num: New 0, Update 221, Delete 0
Unit test Platform: Andriod,Tizen
Andriod test result summary: Pass 221, Fail 0, Blocked 0
Tizen test result summary: Pass 221, Fail 0, Blocked 0